Starter motor runs on and on, but not engaging

[John 535is (Sydney)]

Here's a new one.
Turned the ignition key, the starter motor spins but did not engage. Waiting for 15 seconds, starter still spinning, turn off car, remove key from ignition, starter motor still spinning! Tried restart, no go as starter motor still spinning. Turn off, remove key, open bonnet, yep-its the starter motor whirring all right. After about 60-90 seconds starter motor stops, start car like normal. A week later, same problem. Any idea's how to disengage the starter power next time so I don't burn the motor out?
John535is 1989 (M30)

[Ferret]

Here's a new one.
Turned the ignition key, the starter motor spins but did not engage. Waiting for 15 seconds, starter still spinning, turn off car, remove key from ignition, starter motor still spinning! Tried restart, no go as starter motor still spinning. Turn off, remove key, open bonnet, yep-its the starter motor whirring all right. After about 60-90 seconds starter motor stops, start car like normal. A week later, same problem. Any idea's how to disengage the starter power next time so I don't burn the motor out?
John535is 1989 (M30)

As they're physically sealed units, it wont be possible to push or pull something to stop it running. You'll have to carry a blunt instrument as something to beat the motor with when it starts doing this, and get the solenoid to unstick.

The best way to sort this is just to pull the starter motor completely, easy job on an M30, and take the solenoid and arm apart + clean them up.

[Ross]

The solenoid has seized. Sometimes a weak battery , believe it or not, will cause the solenoid to weld itself together.
Replace the starter solenoid and all will be well.

[Tiger]

Agreed... starter selenoid is bad. Replace it.